It is well known to adapt the floors of vehicles (such as vans, minibuses and coaches) for the releasable and adjustable securing of seats, wheelchairs or other objects or furniture at any of a range of locations with variable position according to need. Typically this is by means of one or more tracks fixed onto or integrated into the vehicle floor. The tracks have an upwardly-open internal channel, usually of extruded aluminium, and the top slot opening of the channel—extending the length of the track—is defined between opposed overhanging flanges or lips.
Articles such as seats are secured to these tracks via releasable anchorage devices—either discrete devices, or incorporated as part of the article to be secured—having inverted-T section (e.g. mushroom-shaped) anchorage formations adapted to be retained by engagement beneath the track flanges. [In what follows, descriptions are presented as for a horizontal, upwardly-open track with the anchorage device above, this being the usual situation, but of course this is not intended to limit the technical meaning unless the context clearly requires it. The tracks and anchorages may be used on walls and ceilings.]
Various kinds of track are in use. The simplest format with a uniform width, parallel-sided top slot requires outwardly-expandable anchorage formations if they are to be insertable from above. Clamping of the anchorage against the track is needed to prevent longitudinal movement.
Another popular track format has the flanges interrupted by a series of uniformly-spaced cut-outs so that the top slot has a series of periodic enlargements, usually of circular outline (so as to be formable by drilling). See FIG. 12. Each flange 91 has a regular series of arcuate cut-outs 94. Opposed cut-out pairs provide enlargements 95 of the track slot at a pitch “x”. Intervening parallel straight flange edge parts 97 define restrictions 96 thereof.
Anchorage devices usable with such track have retaining formations with longitudinally-localised laterally-enlarged bottom parts (feet) and narrower intermediate-height parts (stem), so that they are insertable into the track when the feet are aligned with cut-outs (removal/insertion position) but when slid along through about half a pitch spacing the feet are captive beneath the flanges. One or more such slidable feet then anchor the device against being pulled up away from the track.
It is necessary to hold or lock the device longitudinally in position relative to the track so that the slidable foot cannot slide from the captive position to a removal/insertion position. Usually one or more non-slidable formations are provided, dimensioned to project down into a cut-out but unable to slide through the narrow parts. Such non-slidable protrusions serve to transfer operational longitudinal loads from the anchorage device to the track as well as holding the slidable portion(s) in the captive position.
To be able to engage/disengage both slidable feet and non-slidable protrusions with a track, the anchorage device must provide for relative movement between them. One conventional way is by forming a non-slidable protrusion as a “plunger”, positioned about half a pitch step out relative to the slidable foot portion(s) and movable up and down in the device so that it can be lowered into a track cut-out after the slidable foot portion has been inserted and slid to the captive position. Alternatively it is known to provide a mechanism in the device to shift slidable and non-slidable formations longitudinally relative to one another in the device, changing their spacing from some multiple of the pitch spacing (insertable/removable) to being substantially half a pitch out (captive).
One particular use of current importance for such rail systems is in the securing of seats in vehicles e.g. vehicles designed or adapted for use by elderly and/or disabled people.
Usually two sides of a seat may be rigidly secured down via respective anchorage devices engaging a pair of tracks at either side of the seat. Or, such anchorage devices may be incorporated into a seat base or leg structure.
Anchorage devices for seating have certain criteria. Firstly it is important that at the rear end—that is, the end towards the rear of the vehicle irrespective of the orientation of the seat—the anchorage is strongly resistant to being pulled up out of the track, because that is a primary load in the event of a front-on crash. At the front end, much less pull-up resistance is needed. Adequate longitudinal load resistance must be provided in any event, by distributing the engagement of the device with the track among plural points.
Secondly it is important to avoid “rattle”. The feet fit with clearance in the track channel, so that the devices are easy to insert and slide, and so that distortion and some variations in track dimensions can be accommodated. However play, shifting and rattling are highly undesirable in a seat fitting. Accordingly many known anchorage devices incorporate anti-rattle mechanisms whereby retaining formations in the track channel (such as feet) clamp or grip against the track in the captive position. See GB2219493, GB2315013, EP1892142 and WO2008/113610. Typically a formation of the device is lifted relative to a main body of the device to press or clamp the track flanges vertically, or expanded or shifted laterally to grip or clamp sideways in the channel or top slot. Or, as described in our co-pending application also entitled “Anchorage Systems and Devices”, claiming the priority of GB1000907.4 (20 Jan. 2010) and which is incorporated herein by reference in its entirety, retaining feet may have longitudinally-inclined top surfaces or ramp surfaces which engage or clamp the track flange on simple longitudinal movement and can reduce or eliminate rattle without a lifting mechanism being necessary.
Thirdly it is preferred that a single anchorage device suffices for one side of a seat, so the device body may be quite long. This makes rattling more difficult to inhibit and a track-engaging formation adapted for anti-rattle is preferably provided at some intermediate position along the body of the device, as in the prior art cited above.
Fourthly, however, access to the device is awkward for seat installation. Seats are low at the seat part and overhang at the back, which hinders access to operating members e.g. levers or handles for longitudinal shifting of track-engaging formations or for actuating anti-rattle mechanisms. This ergonomic factor significantly limits the kinds of mechanisms used.